Ready-Made Reading Spectacles Often Fail to Meet Optical Quality Standards

Many ready-made reading spectacles fail to meet optical quality standards, which may potentially lead to unwanted side effects like asthenopia, according to an investigation published in Ophthalmic and Physiological Optics. More robust and standardized manufacturing protocols and public health awareness campaigns may help to lower this prevalence and alleviate these unwanted side effects, the report suggests.

Researchers analyzed 105 ready-made reading spectacles with powers ranging from +1.50 to +3.50 diopters (D) in +0.50 D increments (n=21 for each power) that were purchased in open markets. The team examined the optical quality of the spectacles, which included checking for induced prism and the appropriate safety markings according to International Organization for Standardization (ISO) criteria and a more compromised standard that is frequently used in countries with a lower supply of resources. A centration distance of 62 mm was assumed for spectacles that did not contain the near centration distance, which ISO standards stipulate must be located on the temples of frame front.

All 105 of the ready-made reading spectacles had significant induced horizontal prism that exceeded ISO tolerance levels, the report shows. A total of 30% had vertical prism greater than the specified tolerances, and lenses with a power of +2.50 or +3.50 D were more likely contain excessive vertical prism (48% and 43%, respectively).  

Compared with a less conservative set of standards, which are frequently used in countries with low resources, the prevalence of induced horizontal and vertical prism was reduced to 88% and 14%, respectively. Only 15% of the ready-made reading spectacles had the centration distance labeled and none had any safety markings that were required as per the ISO standards.

The study authors highlight the significance these findings may have on individuals residing in underdeveloped nations.

“Considering the fact that custom-made spectacles for presbyopic correction require financial and technical resources that may not be available in developing countries, low-cost spectacles such as ready-made reading spectacles (ready-readers) are usually considered appropriate alternatives,” the researchers explain.

Study limitations include the absence of average near interpupillary distance data for individuals with presbyopia in this study population.